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Help me pick the right pistons. 78 440 #2639197
03/31/19 02:44 PM
03/31/19 02:44 PM
Joined: Feb 2009
Posts: 110
Grand Forks, ND
cougar_cat_25 Offline OP
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cougar_cat_25  Offline OP
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Grand Forks, ND
Went to freshen up my 1978 440 before slapping on the new trick flow heads and found a cracked ring land. Engine builder has retired and pistons don't have part numbers stamped, so might as well do a set. Current set up with stock heads and cast crank was supposed to have a 9.5 CR (bore:4.350, stroke: 3.75, chamber volume: 92 cc, deck height: 0.10, comp height: 1.988, weight: 860 g, weight with pin: 1122 g). Biggest change will be the 78 cc chamber on the TF heads. My understanding is the aluminum heads would handle the higher comp ratio if I stuck to the same size piston. So hypereutectic or forged? How close to weight do I have to get? For example I found a forged set that weighs 1072 grams with pin. Thanks guys

Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2639204
03/31/19 03:05 PM
03/31/19 03:05 PM
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Arlington, Texas
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bobby66 Offline
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Originally Posted by cougar_cat_25
Went to freshen up my 1978 440 before slapping on the new trick flow heads and found a cracked ring land. Engine builder has retired and pistons don't have part numbers stamped, so might as well do a set. Current set up with stock heads and cast crank was supposed to have a 9.5 CR (bore:4.350, stroke: 3.75, chamber volume: 92 cc, deck height: 0.10, comp height: 1.988, weight: 860 g, weight with pin: 1122 g). Biggest change will be the 78 cc chamber on the TF heads. My understanding is the aluminum heads would handle the higher comp ratio if I stuck to the same size piston. So hypereutectic or forged? How close to weight do I have to get? For example I found a forged set that weighs 1072 grams with pin. Thanks guys



The Sealed Power 2355's would be a good place to start. Small valve reliefs, though....

Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2639227
03/31/19 04:24 PM
03/31/19 04:24 PM
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Posts: 4,309
Prospect, PA
BSB67 Offline
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Prospect, PA
Your old compression ratio was closer to 8.5:1

A 2.06" CD piston with 5 cc valve relief will be 10.3:1 with your TFs.

You'll need to get the weight closer than that.

The 2355 is your best shot at getting the weight right. Everything else will be too light, unless you're willing to rebalance.

Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2639248
03/31/19 05:55 PM
03/31/19 05:55 PM
Joined: Feb 2009
Posts: 110
Grand Forks, ND
cougar_cat_25 Offline OP
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Grand Forks, ND
You're right. I ran those number through a CR calculator and I don't know how he thought it came to 9.5! Valve relief would be a good idea, and 10.3 would be a good number to shoot for.

Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2639256
03/31/19 06:09 PM
03/31/19 06:09 PM
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usa
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lewtot184 Offline
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Originally Posted by cougar_cat_25
You're right. I ran those number through a CR calculator and I don't know how he thought it came to 9.5! Valve relief would be a good idea, and 10.3 would be a good number to shoot for.
you might get a 10.3 number with Icon 836's and take some weight off.

Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2639257
03/31/19 06:10 PM
03/31/19 06:10 PM
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Posts: 2,094
central texas
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krautrock Offline
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central texas
my first look would be the SRP pistons, are you trying to get away without rebalancing?

http://www.jepistons.com/Catalogs/SRP/Mopar/400-440_flat.aspx

Last edited by krautrock; 03/31/19 06:11 PM.
Re: Help me pick the right pistons. 78 440 [Re: krautrock] #2639358
03/31/19 08:31 PM
03/31/19 08:31 PM
Joined: Feb 2009
Posts: 110
Grand Forks, ND
cougar_cat_25 Offline OP
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Grand Forks, ND
Originally Posted by krautrock
my first look would be the SRP pistons, are you trying to get away without rebalancing?

http://www.jepistons.com/Catalogs/SRP/Mopar/400-440_flat.aspx


Local shop that can balance is back up weeks, if not months. Finding a set that balances would save some headache. Thanks

Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2639738
04/01/19 03:49 PM
04/01/19 03:49 PM
Joined: Jun 2016
Posts: 170
Wisconsin
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Medlock51 Offline
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I'm a fan of Racetec/Autotec... they will build anything you want at good prices...2618 or 4032. All forged.

Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2640087
04/02/19 09:18 AM
04/02/19 09:18 AM
Joined: May 2011
Posts: 4,488
northern,Ohio,USA
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Clanton Offline
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Lighter pistons are better than heavier and I think I read that 10 grams +/- would work but all have to be equal weight.The crank should have a balance weight mark on it saying what weight.

Last edited by Clanton; 04/02/19 09:25 AM.

GOTBOOST!New improved with Victor heads.
http://www.enginelabs.com/mopar-big-bloc...t-of-necessity/
Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2640348
04/02/19 07:15 PM
04/02/19 07:15 PM
Joined: Jul 2009
Posts: 489
IL
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EchoSixMike Offline
mopar
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IL
Especially if you're putting decent heads on it later, just bite the bullet now and get modern pistons and a rebalance.

I like the Icon stuff for reasonably priced pistons. You can lose over 200 gms per piston over the stock junk; that alone will be like a new engine, and the bearings and block will thank you. S/F....Ken M

Re: Help me pick the right pistons. 78 440 [Re: cougar_cat_25] #2640583
04/03/19 11:05 AM
04/03/19 11:05 AM
Joined: Jan 2017
Posts: 288
Nevada
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merpar Offline
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Call Glen at Icon pistons, 1-800-648-7970. ext. 159. Icon----United Engine & Machine has been making pistons since 1923.







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